One option that is popular with motor vehicles is cruise control. Cruise control allows an operator of a motor vehicle to set a predetermined speed for the vehicle, and maintains the vehicle at that speed until either the cruise control is turned off, or the brakes are applied.
A motor vehicle typically has a speed sensor mounted on an output shaft of a transmission. The speed sensor provides a series of pulses to a computer. When a vehicle""s speed increases the frequency of the pulses will also increase. There is a concomitant decrease in the frequency of the pulses from the speed sensor when the speed of the vehicle decreases. For a given vehicle speed, there is a correlated frequency of the pulse stream from the speed sensor. The cruise control attempts to maintain the pulse frequency of the desired speed by regulating the accelerator of the vehicle.
The cruise control stores the speed of the vehicle when the cruise control is set to the desired speed. The cruise control receives the pulse stream from the speed sensor and compares the frequency of the pulse stream to the frequency value of the set speed. The cruise control, in response to a difference between the pulse stream from the sensor and the stored set value operates a vacuum controlled diaphragm that is coupled to the accelerator linkage. The accelerator is controlled in order to maintain the pulse stream from the speed sensor as close to the stored value as possible.
It is common for a vehicle operator to use cruise control to maintain a constant speed on a highway. In the event another operator makes a lane change into the path of the vehicle or the vehicle comes upon a slower driver the operator is required to disable the cruise control, typically by stepping on the brake. A problem occurs when the operator is slow to react to the other vehicle and fails to disable the cruise control in time.
In view of the dangers associated with automobile travel, there is an ongoing need or the vehicle comes upon a slower driver the operator is required to disable the cruise control, typically by stepping on the brake. A problem occurs when the operator is slow to react to the other vehicle and fails to disable the cruise control in time.
In view of the dangers associated with automobile travel, there is an ongoing need for enhanced automobile driver aides. One possible area of increased driver aides involves detection of objects in front of a vehicle. As the vehicle approaches objects (e.g. other vehicles, pedestrians and obstacles) or as objects approach the vehicle a driver cannot always detect the object and perform intervention actions necessary to avoiding a collision with the object.
To enhance the safety of trucks, for example, sensor systems or more simply xe2x80x9csensorsxe2x80x9d for detecting objects around a truck have been suggested. Such sensors typically include an optical or infrared (IR) detector for detecting obstacles in the path of the vehicle.
In such an application, it is necessary to provide a sensor capable of accurately and reliability detecting objects in the path of the vehicle.
Radar is a suitable technology for implementing a sensor for use in vehicles such as automobiles and trucks. One type of radar suitable for this purpose is Frequency Modulated Continuous Wave (FMCW) radar. In typical FMCW radar, the frequency of the transmitted CW signal linearly increases from a first predetermined frequency to a second predetermined frequency. FMCW radar has the advantages of high sensitivity, relatively low transmitter power and good range resolution.
Because sensors disposed on vehicles are consumer products that may affect the safety of vehicles, the accuracy and reliability of the sensors are tantamount. Aspects of the sensors which contribute to its accuracy and reliability include its susceptibility to noise and the overall precision with which received radio frequency (RF) signals are processed to detect objects within the field of view of the sensor. Susceptibility to noise for example can cause false detections and, even more deleteriously, cause an object to go undetected.
Further significant attributes of the sensors are related to its physical size and form factor. Preferably, the sensor is housed in a relatively small enclosure or housing mountable behind a surface of the vehicle. For accuracy and reliability, it is imperative that the transmit antenna and receive antenna and circuitry of the sensor are unaffected by attributes of the vehicle (e.g. the vehicle grill, bumper or the like) and that the sensors are mounted to the vehicle in a predictable alignment.
It would, therefore, be desirable to provide a sensor system which is capable of detecting the presence of objects in front of a vehicle and further to detect the speed of these objects. Once this information is obtained the speed of the vehicle can be adjusted to maintain a safe trailing distance behind an object located in front of the vehicle.
In accordance with the present invention, a detection system is utilized to control the speed of a vehicle, known as Adaptive Cruise Control. The system includes a radio frequency (RF) transmit receive (TR) sensor module (or more simply xe2x80x9csensorxe2x80x9d) disposed such that a detection zone is deployed in front of a vehicle. The sensor includes a sensor antenna system which comprises a transmit antenna for emitting or transmitting an RF signal and a receive antenna for receiving portions of the transmitted RF signal which are intercepted by one or more objects within a field of view of the transmit antenna and reflected back toward the receive antenna. A signal antenna can be used for both the transmitting and receiving.
With this particular arrangement, a detection system that detects objects in a region about a front of a vehicle is provided. If the system determines that the vehicle is approaching an object or that an object is approaching the vehicle, then the sensor initiates steps that are carried out in accordance with a set of rules that control the speed of the vehicle. The speed of the vehicle is adjusted to maintain a safe trailing distance behind the detected object, thereby providing an adaptive cruise control function to the vehicle.